Centerless grinder



Jan. 6, 1959 COES, JR 2,867,060

- CENTERPESS GRINDER Filed Nov. 9, 195a 2 Sheets-Sheet 1 INVENTOR 70 72 /55 L B/N6 C065 JE.

ATTORNEY States CENTERLESS GRINDER Loring 'Coes, Jr., Brookfield, Mass., assignor to Norton Company, Worcester, Mass, a corporation of Massachusetts The invention relates to centerless grinders. 7

One object of the invention is to provide a centerless grinder especially adapted for the grinding of long shafts. Another object of theinvention is to grind at a much higher rate of stock removal than heretofore possible. Another object is to provide, in combination with other elements of a centerless grinder, a grinding wheel supporting and rotating apparatus that will permit the grinding wheel to be rotated very much faster than has been heretofore possible, thereby removing stock at a much faster rate. Another object ofthe invention is to provide a dependable and highly practical grinder having the characteristics indicated.

Another object of the invention is to provide a center less grinder which is capable of a wide variety of adjustments, so .as to accomplish grinding with through feeding, infeed grinding, finish grinding as well as rough grinding. Another object is to provide for a wide variety of relative positions of the grinding wheel, the regulating wheel and the. work rest. Another object is to provide a centerless grinder with two grinding stations, one of which .can be a heavy stock removal station, and the other of which can bea finish grinding station, with provision for eliminating one of the stations altogether if desired. Another object of the invention is to provide a centerless grinder having two grinding stations with the grinding wheel components moving relative to the work at different angles so as to break up the grinding lines and produce better finish. Another object is to obtain high stockremoval in a grinder fulfilling the previous object.

Other objects will be part obvious or inpart pointed out hereinafter.

In the accompanying drawings illustrating one of many possible embodiments of basic machine features and several embodiments of'the relative arrangements of parts and the wheels,

Figure 1 is a view partly'in front elevation and partly in'vertical section of-a centerless cording to the invention, v

Figure 2 is a planview of the grinder,-

Figure 3 is a-vertical sectional view taken on the line 3-3 of Figure 1, a

Figure 4 is a plan viewof the grinding'throat with the truing slide in position,

Figure 5 is a front elevation of the grinding throat and" illustrating theswivel table having thetruing slide thereon, 1

Figure 6 is a view partly in section and partly in ele- Figures 9 and 10 illustrate other relative arrangements of the wheels and work rest blade, and

Figure 11 illustrates how an upper work rest blade can be held in position in the grinding throat;

grinder constructed ac- 2,867,060 Patented Jan. 6, 1959 Referring first to Figure 1, the machine base 10 has on the left hand upper side thereof a slideway 11 sup porting a slide 12 having an integral nut 13 through which extends a screw shaft 14 having a hand wheel 15. On the screw shaft 14 are thrust bearings 16 on either side of a bearing bracket 17 which is secured to the base 10 and which journals thescrew shaft 14. Thus the slide 12 can be adjusted in position to the right or left on the machine base. 10. Screws 20 are provided to lock the slide 12 in any position which it can assume. Located a little higher up on the right hand'side of the base 16 is a second slideway 21, supporting a slide 22 having an integral nut 23 through which extends a screw shaft 24 having a hand wheel 25. On the screw shaft 24 are thrust bearings 26 on either side of a bearing bracket 27 which is secured to the base 10 and Reverting to the slide 12 again, and referring to Fig-,

ure 2 as well as 'to Figure 1, the slide 12 supports a vertical slideway 31 supporting a slide 32having a nut.

33 through which extends a screw shaft 34 having a bolt head 35. On the screw shaft 34 is a ball bearing thrust bearing 36 the lower race of which issupported by a boss 37 extending upwardly from and being an integral part of the slide 12. Thus the vertical slide 32 can be raised or lowered by turning the bolt head 35. Screws 40 are providedto lock the slide 32 in any position which it can assume.

Referring again to the right hand side ofFigure 1 and referring also to the right hand side of Figure 2, integral with the slide 22 and extending upwardly therefrom is a column 41 having a cylindrical bore-i2 in which fits a large trunnion 43. A wheel head 44 is cut to fit over the column 41 and has bores 45 nicely fitting the trunnion 43. The trunnion'43 has a head 46 by. which it may be clamped to the wheel head 44 by means a wheel head, is a powerful electric motor 51 on the armature shaft 52 0f which and securedjthereto is a multiple V pulley 53. Multiple V belts 55 connect. the pulley 53 to a pulley 57. The ratio of vthe diameter of the pulley 53 to that of pulley 57 is intended to be 1.87:1. Of course within the scope of theinventionany ratio whatsoever can be used but, as willybellateriexa plained, it is contemplated that the grinding wheel spindle 60 on which the pulley 57 is mounted and to which it' is secured will be drivenat a very high rate of speed.

The wheel spindle 60 has a small diameter portion 61 to which the pulley 57 is secured, a larger diameter portion 62 which is threaded at the left hand end 63, and Y a still larger diameter threaded portion 64 to the right of the portion 62. The inner race 65 of a ball bearing is held between a nut 67 and a sleeve 68 on the portion 62 while the inner race 69 of a ball bearing is held between the sleeve 68 and the threaded portion 64. By tightening the nut 67, which may be a spanner nut as shown, the inner races 65 and 69 are securely held to the 'spindle60.

The outer race 71 of the ball bearing having theinner race 65 is held between a shoulder at the end of a cylindrical bore 72 through which the spindle 60 extends and a ring 73 bolted to the left hand outside of the slide 32. The outer race 75 of the ball bearing of the inner race 3 69' isheld. in placebetweena. shoulder at the right hand end of the bore 72 and a plate 77 bolted to the right hand outer side of the slide 32. Thus is the spindle strongly journaled in the slide-wheel head 32 which is massive, and theball bearings allowrotation of the spindle 60 with little friction.

To the right of the threaded portion 64 of the spindle 60 isa reduced diameter portion 80 to the right of which is a threaded end 81. of the spindle 60. Mounted on the portion80is a wheel holding plate 82 which is held in place by a nut and washer 83 on the threaded end 81. Bolts 85 located in the plate 82 are secured to abrasive segments -which collectively constitute a grinding wheel, the grinding surface being the plane end faces of the segments 90. The wheel is referred to as a cup wheel, which simply means it has an annular grinding face.

Referring nowto Figure 3 as well as-to Figure 1, I provide a wheel holder 95. to hold the segments inplace, against'centrifugal force. This is shown as having the shape of-a hollow cylinder with an integral back plate 96 having ahub 97 that fits on the threaded portion 64 and has a key portion 98 fitting in a spline 99 in the portion 64. The wheel holder drives the segments 90 by means of integral lugs 100 which extend into spaces formed by cutting notches 101 in the outer corners of the segments 90. This wheel holder 95 can be moved to the left to maintain portions of the segments 90 projecting beyond the Wheel holder 95 after the segments have Worn so as to require such movement, by backing off a spanner nut 105'and turning a cup-shaped nut 106, both of which nuts are on the threaded portion 64, as the cup-shaped nut.106 has pins 107 projecting into a groove on the outside of the hub 97.

If the motor 51 turns at 3,400 R. P. M. and the ratio as stated between pulleys 53 and 57 is 1.87:1, the spindle 60 will be turnedat 6,358 R. P. M. In the illustrative embodiment of this invention the. wheel made up of the segments 90 is 14" in diameter and the segments are 2" thick. This gives a velocity of the midpoints v =Gr" for centrifugal force and the equation:

G'==32'g to convert to gravitational units and where: G=centrifugalforce v=velocity infect per second r=radius in feet gravitational units we have the combined equation:

It therefore comes out that the centrifugalforce is equal to 6,944 gravitational units which simply means that each pound of the segments at the midpoint is under a radial force of 6,944 pounds. This, while high, can be readily withstood by the construction shown. The wheel holder 95 can be made of; strong steel such as nickel steelto withhold the centrifugal force with but a small portion of the segments 90 projecting beyond the front of the. wheelholder 95. The segments 90 should be made of strong abrasive. of which the best example. that I know is the phenol-formaldehyde 1 resin bonded abrasive composition the manufacture ofwhich is now so well known and has been described in so many patents, including my own, that it is unnecessary here to describe same since. this invention. deals. with a machine. Such phenolic resin bonded segments can be obtained from any manufacturer of grinding wheels and abrasives. The wheel holder 95 should, however, cover more than three quarters of the periphery of the grinding wheel axially at the commencement of grinding, as shown.

I have calculated the tangential stress in pounds per square inch on the wheel holder 95 on the assumption that it is one inch thick; There are two' parts to this calculation, one for the centrifugal force of the abrasive segments, and the other for the centrifugal force of'the wheel holder itself. For the segments, the averagecentrifugal force factor in gravitationalunits was taken as 6,944. In accordance with the known way of making this calculation, a diametral piece of the material in question of unit width, in this case an inch, and of the thickness of thewallof the. hollow cylinder. is: the body which, in the field of force; constitutes. the. mass. involved. Thisassumedbody; is 14" long: and.2 thick. The weight ofeach cubic. inch: is; figured .fromthe specific gravity; of the'abrasive, which is taken as.2.5- and the mass of a cubic inch of. water which is taken as .036 pound. The width and the thickness cancel out. Thus the tangential stress in the steel wheel holder due to the centrifugal force of the segments is found to be:

6,944 X l4 215 X 036281750 lbs/sq.- in.

The calculation for the tangential stress in poundsper square inch on the Wheel'holder. 95 due. to its.own centrifugal forceis as follows:

T he multiplier 7.5/ 6 was used to increase the centrifugal force due to the increased diameter of the holder and the average diameter was taken as in the first case. Similarly the length of apiece. was taken asI 16'insteadof 14" because of the increase. of diameter. Figure 7.86 is the specific gravity of iron, whicluwill' do. for. steel althoughitis a little high. These calculations are both of them close approximationsasno.moreisneeded. It turns out that-the total tangential. stress in pounds per square inch onthe wheel holder 9S-is equal to the sum of the foregoing stresses which! isv 36,750 pounds per square inch. But there are steels which-have a. tensile strength of.320,000 pounds per. square; inch giving a:factor of safety of a little better.than-8.7;t0. whi hzshmlld be adequate. Furthermore the wheel holder.-95. could readily. be. made 2, 3, or even-.4 inches .thick enablingthe wheel of segments 90 to be driven at much higher speeds. An estimateis that speeds as great as- 50,000 surface feet per; minute can be achieved. Insuch case the'segments should-be allowed to' overhang the wheel. holder by only a small amount for example /s At 20,000 surface feet per minutethe. overhang can be much greater inorder tocausefewer stoppages to-- withdraw the-nut 105 and back off the nut 106.

Referring nowto the. right handside of Figures 1 and 2, mounted upon the wheel head 44 is an'electric motor 110 which, for example, may turn at 1,150R. P. M. The armatureshaft 111 of this motor 110'has secured thereto a multiple V pulley 112 which, by means of multiple V belts 1 13' drives a pulley. 114 at one end ofa Vicker speed change unit.120 which. drives a multiple V pulley 121 that, by means of multiple V belts 122, drives a multiple, V pulley 123 which: is secured-:to the spindle 124 of avregulating-wheel' 125. The spindle-124 is journaled'in theiwheel.head.44rby means ofJa-bearing box 126 on the front side ofthe: wheclhead 44' and a bearing box 1310 on-a' removable plate131' secured by means of bolts 132 to the rear side of the: wheel head when desired. These. wheels can bethe usual rubber bonded Wheels.

The Vicke'rs unit 120 is available on the market and hence need not be described and besides it belongs to another field of engineering. It is controllable by means of a wheel 135 to cause the output pulley 121; to be rotated between the limits of zero and 1,150 R. P. M., assuming the motor 110 is'a 1,150 R. P. M. motor, the pulleys 112 and 114 being shown as of the same diam eter. With a reduction ratio of 111.8 from the pulley 121 to the pulley 123 the latter can be driven from a speed of zero to a speed of 639 R. P. M. .This enables the regulating wheel 125 to be driven, when it is of full diam-. eter which in this case is 12", at from zero to 2,000 sur face feet per minute. I now prefer a surface speed for the regulating wheel 125 of 1,000 feet per minute and the construction above described will readily achieve this at all working diameters of the regulating wheel 125, which can be rubber bonded wheels.

Referring now to Figures 1, 2, 4, 5, and 6, the base has, between the slideways 11 and 21, a platform 140 whose top is a horizontal plane and has a conical depression 142 therein. A swivel table 145 rests upon the platform 140 and has an integral downwardly extending conical projection 147 extending into the conical hole 142.

Extending upwardly from the right hand side of the platform 140 is a bracket 150 whose upper end is drilled and tapped to form a nut 151 through which extends a screw 152 having a knurled wheel 153. Integral with the screw 152 and extending beyond it is another screw 154 with threads of the opposite hand. This screw 154 extends through a nut 155 integral with the swivel table 145. Turning the knurled head 153 swings the swivel table.

The swivel table 145 is to be moved through very small angles only, a matter of one degree or even minutes of arc. For this reason the fact that there would be some binding of the screws 152 and 154 if large movements were attempted is wholly' immaterial because up to two degrees of are there would be no binding. The threads of one of the screws 152 and 154 has a slightly greater pitch than the other one which gives a Vernier effect to make delicate adjustment possible. One more note about this mechanism is that the way to get the screw 152 inside of the integral nut 151 is, after drilling and tapping the latter, to cut it on the horizontal diameter,

insert the screw 154 into the nut 155, place the cut off half of the nut 151 on top of the lower half that is part of the bracket 150, with some strips of solder inbetween, and then solder the two halves together.

After adjustment of the table 145 to its zero position or to the desired small angle say 30 minutes of are resulting from drawing the nut 155 to the right, the table 145 is locked in position by tightening bolts 157 which extend through slightly oversized holes through end portions 158 of the table 145 and into threaded holes in the platform 140. Formed upon the top of the swivel table 145 are horizontal table and slide ways 160 for the support alternativelyof a work rest table 165, Figures 1, 2, and 3, and a truing slide 170, Figures 4, 5, and 6. The work rest table 165 has complementary ways fitting the ways 160 with a gib 171 which can be tightened by set screws, not shown, to lock the table 165 in position. The table 165 is simply slid into position on the swivel table 145 and then locked, the ,slide 22 having first been moved to the right to permit. this to be done. The table 165 should be pushed all of the way backward until it contacts a bracket 174 having a nut portion 175, and then the gib 171 should be tightened.

Y Adjustably secured to the side tion of the table 165 by means of bolts 177 is a work rest blade 180. This and otherswith which it may be replaced extend through the grinding throat and support work pieces W which usually are long shafts. A hold down arm 185 is provided at the far end of the grinding throat to prevent the work piece W fromrisingthere duev of an upstanding porto the upward force imparted by the grinding wheel and this has a beveled front edge. So firmly does the downwardly moving front side of the grinding wheel 90, however, hold down the work piece W that it rarely presses against the arm 185. in this connection two outboard roller carriages known in the art and which need not be connected to the grinder at all can be supplied for supporting a work piece shaft so that its own weight will have no tendency to cause it to pivot on the blade 180 and rise therefrom. The hold down arm has a square vertical hole by which it is supported on a square shaft 187 extending upwardly from the table 165 and the arm is adjustably secured in position by tightening a bolt 188.

In my grinder the unusual condition is found that, at one side of the grinding wheel 90h is moving downwardly where it contacts the work piece and the regulating wheel 125 is also moving down where (everywhere) it contacts the work piece. This is unusual but has clear advantages, among others it enables the use (or is the resultant of the use) of a cup shaped grinding'wheel 90 as shown. From this point of view the fact that the grinding wheel is segmented is irrelevantbut having a segmented grinding wheel vastly increases the resistance to fracturing strains.

At the front of the machine, rotationally relative to a work piece in the grinding throat the grinding wheel 90 and the regulating wheel 125 are moving in opposite is greater than sliding friction. But in such grinders the two wheels rotationally relative to a work piece in the grinding throat are moving in the same direction. The

regulating wheel acts as a brake, the grinding wheel is trying to over drive the work piece, but cannot do so to any great extent because of the condition of starting friction at the contact between the regulating wheel and the work piece. But at the commencement of grinding of a shaft in mymachine, the regulating wheel is a driving wheel which drives the Work piece against the opposing movement of the grinding wheel. And the joker is that when a work piece shaft is introduced 'intomy grinder, there is no initial condition of starting friction, but the grinding wheel grinds and the regulating wheel regulates, contrary to normal expectation.

The resultant thrust upon a work piece W in the grinding throat is entirely due to the frictional force produced by the grinding wheel 90, since, although the regulating wheel 125 grips the work piece tightly enough to overcome the force generated by the grinding wheel, it acts like a track. The actual grindingthrust upon the work piece is proportional to the pressure between them which is a function of the amount of stock being re moved which is determined by the setting of the slides.

12 and 22 and the swivel angle hereinafter explained.

One definition of one feature of my invention is that,

in mechanical couple, the relative vectoral movement of pass. Even if the swivel angle is such that there is only one grinding station on the cup wheel, this relative vectoral movement results in high stock removal because 7 of the resultant relative velocity increase. And this is important because otherwise increase of velocity results in increase of centrifugal force, which has been dealt with heretofore.

The foregoing definition is stated in proper scientific language but to explain further, an ordinary infeed centerless grinder with the regulating wheel at a zero skew angle represents a case where the vectoral movementof the wheels past the work piece is, as a couple, zero degrees, and in the case of a through feedcenterless grinder, where there is a real skew angle, usually not more than. five degrees, the vectoral movement, as a couple, is the same as-the skew angle (of the regulating wheel). But it should be observedthat, in my grinder, the grinding wheel too has or can have, by adjustment of the slides, a skew angle which can be very substantial. The difference between my grinder, therefore, and any ofwhich I am aware, is very substantial and-result in far greater production in shaft grinding.

In order to provide a through feeding component to the work piece shaft W, the regulating wheel head 44 is set at a skew angle as shown in Figure 3. (:This skew angleis not illustrated in Figures l and 2 because of the greatdifiiculty of drawing the parts. at an angle.) This requires that the regulating wheel 125 be trued to a by perboloid or nearly such. For a discussion of the proper shape of a regulating wheel see the patent to George Crompton, No. 2,459,923. pieces to the rear.

Referring now to Figures 4, 5, and 6, when it is desired to true the regulating wheel 1'25 toform a hyperboloid thereof or to true it after it has become worn, or when it is desired to dress or true the grinding wheel 90, the work rest table 165 is removed by loosening the gib 1'71, withdrawing the slide 22, and then simply pulling the table 165 off of the table 145. The truing slide 17i) also has ways complementary to the ways 160 and it is then started along these ways. slide 170 is a screw shaft 190 held relative to the slide 170 by means of a collar 191 and a hand wheel hub 192 of a hand wheel 193. After the slide 170 has been started along the ways 160 the screw shaft 190 enters the nut portion 175 of the bracket 17% and then turning of the hand wheel 193 feeds the slide 170 slowly through the grinding throat. The slide 170 has a diamond truing tool 195 to true the regulating wheel 125 and a diamond truing tool 196 for truing the grinding wheel 91 Usually one wheel will be trued at a time. Either slide 12 or 22 can be moved to the proper position for truing the wheel 90 or for truing the wheel 125 by first loosening the screws 29 or 36 and operating the hand wheel or 25. Before truing the regulating wheel 125 it is first set to the desired skew angle by turning the bolts 48.

A tapered hyperboloid can be formed of the regulating wheel125 and normally will be by loosening the bolts 157 and turning the knurled wheel 153. As previously explained this taper will be very small. For truing the grinding wheel'90 the swivel table 14 5 should be set at zero angle. When grinding, the swivel table 145 should be set at or approximately at the angle at which it was set for truing theregulating wheel 125. If it is desired that all of the grinding shall be done at the front of the throat, the regulating wheel 125 can be trued, that is shaped, with the slide 145 at zero or even a slightly negative angle, and the slide kept at that position while grinding. When the nut 155 is to the right of dead center, the swivel angle is positive. When it is to the leftv of dead center, the swivel angle is negative. This anglecan be read by the scale and lubber line shown in Figure 1.

From consideration of the Crornpton patent above referred to, it will be seen that a regulating wheel trued as above described will be slightly overlarge at the ends, butby a very small amount and this is an advantage in this invention since it is the ends of the regulating wheel 125 which suffer the wear.

By adjustment of the swivel angle, it is possible to have all the grinding done at the station at the entrance end of the throat, or all of it done at the station at the exit end of the throat, or at both stations in any proportion. In most cases the swivel angle willbe set so that the entrance station will be a stock removal grinding station and the exit station will. be a finish. grinding station.

The adjustments including the various slides are such as to make the machine herein described very versatile.

The skew shown feeds work Extending through the truing are broken up. However, where.v the best finish is not.

wanted but highspeed production is the prime requisite, the setting shown. in Figure 1. will be, preferred, as the off axial thrust on the grinding wheel and spindle gen erated by the setting shownin Figure 7 will cause. a lighter cut to be taken to avoid undue wear. on the-bearings of the wheel spindle 60. But sometimes high produce tion is wanted and sometimes a slightly lower production with a fi'ne finish is wanted, so the versatility of the machine is an advantage.

Figure 8 shows an arrangement with two. work rest blades 200 and 201 with the front of" the grinding wheel moving upwardly, insteadvof downwardly. The thrust at the frontend of thethroat on the shaft W is upwardly and at the rear end of the throat is downwardly. This gives" an advantage of less wear onthe work rest blades. it re-' because the principal thrust is against gravity. quires, however, that the work rest blades be adjusted more carefully. I prefer the arrangement of the illustrated embodimentvof the invention described in connection with Figures 1 to 7 inclusive but in some cases the arrangement of Figure 8 may be preferred.

While in most cases I prefer that the grinding wheel shall move contra to the regulating wheel rotationally relative to the work piece at the principal station, many of the advantages of'the invention will be secured which ever way the wheels rotate. Within the. broad scope of certain features of the invention grinding wheels of other shapes could be used, and I would still prefer that the wheels should move contra to obtain extra stock removal. But as the Vickers unit is capable ofreversing the direction of drive with variations of speed in either direction I have thereby illustrated and described a centerless grinder in which the regulating wheel can be rotated in either direction. Furthermore, by changing the wiring of a motor and in other manners known to the art it can be made to rotate in either directionand consequently within the scope of the broad disclosure hereof the grinding wheel 90 is to be considered to be rotated in either direction as desired.

The arrangement of a cup shaped grinding wheel opposite an hyperbolic regulating wheel the hyperbolic face of which contacts the workpiece and with the regulating wheel axis perpendicular to the grinding wheelaxis or nearly so constitutes one of the features of the invention, and another feature is the provision ofthe wheel holder 95 as described.

Figures 9 and 10 illustrate two other relative arrangements of the wheels and work rest, the Figure 9 arrangement being secured merely by adjustment of the machine that has been described and Figure 10 representing a modification along the lines of Figure 8. In Figure' 9 there is no hold down arm 185 because the regulating wheel is above the work piece W, that is' to saythe line of tangency between them is above the horizontal center line of the work piece W with the grinding face of the wheel 90 vertical. This position achieved by adjustment is in some respects preferable to the relative, arrangement shown in Figure 1 but it requires no change in the machine and the arm can be readily removed by loosening the bolt 188 and pulling it off the square shaft 187; In some machines this square shaft 187 would be omitted altogether. The arrow on the holder 95 indicates the direction of movement of the front portion of the wheel 90. It hardly needs sayingthat when the front portion of the wheel is moving downwardly the rear portion of the wheel is moving upwardly and vice versa.

In Figure 10 the front portion of the wheel 90 is movingupwardly, and the work rest 200 is above the work piece W, but the work piece W is locked in position by a relative arrangement of the parts which brings -the wheel 125 below the work piece W. The work rest blade 200 is supported, asshown in Figure 11, by blocks 205 on square shafts 187;extending upwardly from the work rest table 165. I

The locking'of the work piece in the grinding throat at both stations as illustrated in Figures 9 and which, so far as Figure 9 is concerned, is done simply by adjustment of the machine of Figures 1 to 6, presents the advantage of greater precision because it eliminates the functional reason for the arm 185 and thus the work piece is held by the same three elements everywhere instead of a particular three at one station and another three at the other station, and the former arrangement promotes precision. But the setting shown in Figure 1 has the advantage that, as the work piece is reduced in diameter, the pressure between it and the wheels is lowered less than in the setting of Figures 9 and 10, as will be seen :by a study of the angles of the tangency between the work piece and the wheels which, in the setting of Figure 1 stay more nearly parallel as the work piece is reduced in diameter.

vWhen the regulating wheel is truedby the straight line truing mechanism described herein which, so far as straight'line movement of the diameter is concerned is conventional, the regulating wheel becomes an hyperboloid and thesurface of an hyperboloid is hyperbolic. But there are hyperbolic surfaces not found on hyperboloids and if the regulating wheel is trued according to the Crompton patent other hyperbolic surfaces are formed. At all events the regulating wheel should, when through feed grinding is being done, have a hyperbolic surface or nearly so, except that when only rough grinding is wanted and the regulating wheel surface is narrow, it may have almost any shape provided it is round.

It will thus be seen that there has been provided by this invention a centerless grinder in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth, or shown in the accompanying drawings, is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A centerless grinder comprising a cup shaped grinding wheel having a plane annular grinding surface, a work rest extending substantially parallel to said plane annular surface so that the geometrical projection of its top onto said plane surface defines two separated areas on the annular surface, a regulating wheel component opposite one of said areas forming with the area and part of the work rest a grinding station throat, a regulating wheel component opposite the other of said areas forming with the area and part of the work rest another grinding station throat, means to journal and to rotate the grinding wheel and means journalling the regulating wheel components for rotation, whereby grinding will be done at both grinding station throats.

2. A centerless grinder according to claim 1 having adjustable means supporting the work rest movable to vary the amount of grinding done at each station throat.

3. A centerless grinder according to claim 2 having also a truing tool, a slide to guide the truing tool, means to move the truing tool on the slide in contact with the regulating wheel components, and means to adjust the slide to true off more of one regulating wheel component than the other, whereby to vary the amount of grinding done at each grinding station throat.

4. A centerless grinder according to claim 3 having a mounting for the journalling means for the regulating wheel components which is angularly adjustable about an axis substantially perpendicular to the plane annular grinding surface of the grinding wheel whereby to set grinding surface of the grinding wheel whereby to set the components at a skew angle-to feed workpieces through the grinding station throats. w 5. A centerless grinder according to claim 4 in which the plane annular grinding surface the work rest and the regulating wheel components are so located relatively to each other that a work piece'engaging the grinding surface the work rest and one of the regulating wheel components is locked in position except for axial movement.

6. A centerless grinder according to claim 1 having also a truing tool, a slide to guidethe truing tool, means to move the truing tool on the slide in contact with the regulating wheel components, and means to adjustthe slide to true off more of one regulating wheel component than the other, whereby to vary the amount of grinding done at each grinding station throat.

7. A centerless grinder according to claim '6 having a mounting for the journalling means for the regulating wheel components which is angularly adjustable about an axis substantially perpendicular to the plane annular grinding'surface of the grinding wheel whereby to set the components at a skew angle to feed work pieces through the grinding station throats.

8. A centerless grinder according to claim 7 in which the plane annular grinding surfacethe work rest and the regulating wheel components are so located relatively to each other that a work piece engaging the grinding surface the work rest and one of the regulating wheel components. is locked in position except for axial movement.

9. A centerless grinder according to claim 1 having a mounting'for the journalling means for the regulating wheel components which is angularly adjustable about an axis substantially perpendicular to the plane annular the components at a skew angle to feed Work pieces through the grinding station throats.

10. A centerless grinder according to claim 9 in which the plane annular grinding surface the work rest and the regulating wheel components are so located relatively to each other that a work piece engaging the grinding surface the work rest and one of the regulating wheel components is locked in position except for axial movement.

11. A centerless grinder according to claim 1 in which the plane annular grinding surface the work rest and the regulating wheel components are so located relatively to each other that a work piece engaging the grinding surface the work rest and one of the regulating wheel components is locked in position except for axial movement.

12. A centerless grinder according to claim 11 having adjustable means supporting the work rest movable to vary the amount of grinding done at each station throat.

13. A centerless grinder according to claim 12 having also a truing tool, a slide to guide the truing tool, means to move the truing tool on the slide in contact with the regulating wheel components, and means to adjust the slide to true ofi more of one regulating wheel component than the other, whereby to vary the amount of grinding done at each grinding station throat.

14. A centerless grinder according to claim 1 having a mounting for the journalling means for the regulating wheel compo-nents which is angularly adjustable about an axis substantially perpendicular to the plane annular grinding surface of the grinding wheel whereby to set the components at a skew angle to feed work pieces through the grinding station throats, having also adjustable means supporting the Work rest movable to vary the amount of grinding done at each station throat.

15. A centerless grinder according to claim 14 in which the plane annular grinding surface the work rest and the regulating wheel components are so located relatively to each other that a work piece engaging the grinding surface the work rest and one of the regulating wheel components is locked in position except for axial movement.

, 16. A centerless grinder according to claim 1 in which the plane annular grinding surface the work rest and the tooLmeans to move the truing tool on the slide in contact with the regulating Wheel components, and means to adjust the slide to true ofi more of one regulating wheel component than the other, whereby to vary the amount of grinding done at each grinding station throat.

17. A centerless grinder comprising a grindingwheel having a plane grinding surface, means to journal and to rotate said grinding wheel, a Work rest extending substantially parallel to said plane surface from a ptacc where the surface is moving in one direction relative to the rest in an up and down sense to a place where the surface is moving in the opposite direction relative to the rest in an up and down sense, a pair of regulating wheel components one opposite the work rest where the grind ing wheel is moving in one direction and the other opposite the work rest where the grinding wheel is moving in the other direction and with the Work rest and the grinding wheel forming two grinding station throats said regulating wheel components having peripheral surfaces opposed to said plane surface, whereby to grind at two stations at the same time.

. 18. A-centerless grinder according to claim 17 in which the relative vector-a1 movement-of the grinding wheel surface'and of one of the peripheral surfaces of one 'of the regulating wheel components past the work-res'tisas a couple from 180 degrees to 135 degreesr 19. A centerless grinder according to claim 18 in which the grinding wheel is made up of segments and said grinder having a holder peripherally engaging the grind ing Wheel and capable of sustaining a total tangential stress of greater than 36,750 pounds to the square inch.

20. A centerless grinder according to claim 17 in whichthe grinding wheel is made up of segments and said grinder having a holder peripherally engaging the grinding wheeland capable of sustaining a total tangential stress of greater than 36,750 pounds to the square inch.

References Cited in the file of this patent UNITED STATES PATENTS 1,440,639 Smith .Q Jan. 2, 1923 1,456,462 Reeves May 22, 1923 1,924,588 Addison Aug. 29, 1933 2,224,423 Binns Dec. 10,1940 2,229,281 Ekholm Jan. 21,1941 2,322,6l9 Ekholm June 22, 1943 FOREIGN PATENTS 300,808 Germany Sept. 18, 1917 

